A variable radius roll test for measuring the adhesion of paint systems to deformable steel substrates

A test is developed for measuring the adhesion of paint to the deformable metal substrates used as cladding in automotive and building applications, and also in domestic appliances such as refrigerators and washing machines. The test is based on the application of a stiff overlay to the paint consisting of 1-3mm of epoxy resin, and the sample is tested by rolling the substrate away from the overlay using a variable radius roll of well defined radius. No special substrate preparation is required prior to coating allowing for commercial material to be tested. The paint stiffness is not critical to the performance of the test, so the test should better reflect the toughness or adhesion of the paint than other common tests such as T-bend and reverse impact. Experimental studies show that the test has high sensitivity to differences in paint adhesion/cohesion, even when the adhesion is high. Some analysis of the test mechanics is also presented, including FEA studies.